Rechargeable batteries may be used to store and supply electricity in various applications. Examples of rechargeable batteries include lead acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer), among others.
In some examples, rechargeable batteries may degrade if overcharged, e.g., if a voltage across a battery rises above a predetermined threshold during charging. Likewise, batteries may degrade if overdischarged, e.g., if a voltage across a battery falls below a predetermined threshold during discharging. Thus, various battery management systems may be employed to monitor rechargeable batteries during battery charge and/or discharge cycles so as to reduce battery degradation due to overcharging or overdischarging.
One such approach, e.g., as described in U.S. Pat. No. 5,268,630, includes sampling battery voltage at a fixed rate, and selectively utilizing more or less data samples over time to identify a charging status of the battery.
However, the inventors herein have recognized that there may be a large number of cells included in a battery, and degradation may occur on a per-cell voltage level, e.g., in the context of a battery system powering a vehicle. As such, in order to reduce electronic hardware requirements, the same analogue to digital converter may be used to sample voltages of a plurality of cells. For example, by changing a rate at which an analogue to digital converter is coupled among a plurality of cells, it may be possible to obtain faster samples when needed, while also enabling reduced use of analogue to digital converter hardware.
The inventors herein have also recognized that battery management systems which monitor the cells of one or more batteries may be at least partially powered by said batteries. Thus, such battery management systems may reduce an amount of energy stored in the one or more batteries. For example, when a battery management system performs a measurement on a cell in a battery, an amount of energy may be drawn from said battery. Additionally, energy may be drawn from the battery when a battery management system communicates measurements or other diagnostic information over a communication bus. Further, such measurement communications may reduce available bandwidth on a communication bus. Such parasitic energy consumption by a battery management system may result in a substantial reduction in availability of energy stored in the batteries, particularly in battery systems employing a plurality of cells. Further, such bandwidth reduction may reduce operational efficiency of battery management systems.
In one example approach, a method for switching sampling of battery cells of a battery pack is provided. The example method comprises: adjusting a rate at which different battery cells of a battery cell stack are in communication with an analog to digital converter, where said rate is adjusted in response to a condition of a battery cell. For example, a rate at which different battery cells of a battery cell stack are in communication with an analog to digital converter may be adjusted based on a temperature and/or state of charge of a battery cell, so that faster data sampling can be provided at higher temperatures, for example.
In this way, parasitic energy consumption by a battery management system may be reduced resulting in an increase in an amount of available energy stored in the batteries while at the same time obtaining faster samples when needed, while also enabling reduced use of analogue to digital converter hardware. For example, the number of times energy is drawn from battery cells by a battery management system for measurement purposes may be reduced. Additionally, the number of communication messages which use battery power to drive a communication bus may be reduced leading to an increase in available bandwidth on a communication bus.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.